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//! ## `debug_assert!` for your memory usage //! //! **Please note**: This crate has been deprecated in favor of [alloc-counter](https://crates.io/crates/alloc_counter). //! //! This allocator is a helper for writing high-performance code that is memory-sensitive; //! a thread panic will be triggered if a function annotated with `#[no_alloc]`, //! or code inside an `assert_no_alloc!` macro interacts with the allocator in any way. //! Wanton allocations and unforeseen drops no more - this library lets you focus on //! writing code without worrying if Rust properly managed to inline the variable into the stack. //! //! Now, an allocator blowing up in production is a scary thought; that's why QADAPT //! is designed to strip its own code out whenever you're running with a release build. //! Just like the [`debug_assert!` macro](https://doc.rust-lang.org/std/macro.debug_assert.html) //! in Rust's standard library, it's safe to use without worrying about a unforeseen //! circumstance causing your application to crash. //! //! # Usage //! //! Actually making use of QADAPT is straight-forward. To set up the allocator, //! place the following snippet in either your program binaries (main.rs) or tests: //! //! ```rust //! use qadapt::QADAPT; //! //! #[global_allocator] //! static Q: QADAPT = QADAPT; //! //! fn main() { //! # // Because `debug_assertions` are on for doctests in release mode //! # // we have to add an extra guard. //! # if qadapt::is_active() { //! assert!(qadapt::is_active()); //! # } //! } //! ``` //! //! After that, there are two ways of telling QADAPT that it should trigger a panic: //! //! 1. Annotate functions with the `#[no_alloc]` proc macro: //! ```rust //! use qadapt::no_alloc; //! use qadapt::QADAPT; //! use std::panic::catch_unwind; //! //! #[global_allocator] //! static Q: QADAPT = QADAPT; //! //! // This function is fine, there are no allocations here //! #[no_alloc] //! fn do_math() -> u8 { //! 2 + 2 //! } //! //! // This function will trigger a panic when called //! #[no_alloc] //! fn does_panic() -> Box<u32> { //! Box::new(5) //! } //! //! fn main() { //! do_math(); //! //! let err = catch_unwind(|| does_panic()); //! # if qadapt::is_active() { //! assert!(err.is_err()); //! # } //! } //! ``` //! //! 2. Evaluate expressions with the `assert_no_alloc!` macro //! ```rust //! use qadapt::assert_no_alloc; //! use qadapt::QADAPT; //! //! #[global_allocator] //! static Q: QADAPT = QADAPT; //! //! fn main() { //! // This code is allowed to trigger an allocation //! let b = Box::new(8); //! //! // This code would panic if an allocation occurred inside it //! let x = assert_no_alloc!(*b + 2); //! assert_eq!(x, 10); //! } //! ``` #![deny(missing_docs)] // thread_id is necessary because `std::thread::current()` panics if we have not yet // allocated a `thread_local!{}` it depends on. use thread_id; // Re-export the proc macros to use by other code pub use qadapt_macro::*; use spin::RwLock; use std::alloc::GlobalAlloc; use std::alloc::Layout; use std::alloc::System; use std::thread; thread_local! { static PROTECTION_LEVEL: RwLock<usize> = RwLock::new(0); } static IS_ACTIVE: RwLock<bool> = RwLock::new(false); static INTERNAL_ALLOCATION: RwLock<usize> = RwLock::new(usize::max_value()); /// The QADAPT allocator itself /// /// To make use of the allocator, include this code block in your program /// binaries/tests: /// /// ```rust /// use qadapt::QADAPT; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// fn main() { /// # if qadapt::is_active() { /// assert!(qadapt::is_active()); /// # } /// } /// ``` #[deprecated( since = "1.0.3", note = "Please use the `alloc_counter` crate instead." )] pub struct QADAPT; static SYSTEM_ALLOC: System = System; /// Let QADAPT know that we are now entering a protected region and that /// panics should be triggered if allocations/drops happen while we are running. /// /// **Example**: /// /// ```rust /// use qadapt::enter_protected; /// use qadapt::exit_protected; /// use qadapt::QADAPT; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// fn main() { /// // Force an allocation by using a Box /// let x = Box::new(2); /// /// enter_protected(); /// // We're now in a memory-protected region - allocations and drops /// // here will trigger thread panic /// let y = *x * 4; /// exit_protected(); /// /// // It's now safe to allocate/drop again /// let z = Box::new(y); /// } #[deprecated( since = "1.0.3", note = "Please use the `alloc_counter` crate instead." )] pub fn enter_protected() { #[cfg(debug_assertions)] { if thread::panicking() || !is_active() { return; } PROTECTION_LEVEL .try_with(|v| { *v.write() += 1; }) .unwrap_or_else(|_e| ()); } } /// Let QADAPT know that we are exiting a protected region. Will panic /// if we attempt to [`exit_protected`] more times than we [`enter_protected`]. /// /// **Example**: /// /// ```rust /// use qadapt::enter_protected; /// use qadapt::exit_protected; /// use qadapt::QADAPT; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// fn main() { /// // Force an allocation by using a Box /// let x = Box::new(2); /// /// enter_protected(); /// // We're now in a memory-protected region - allocations and drops /// // here will trigger thread panic /// let y = *x * 4; /// exit_protected(); /// /// // It's now safe to allocate/drop again /// let z = Box::new(y); /// } #[deprecated( since = "1.0.3", note = "Please use the `alloc_counter` crate instead." )] pub fn exit_protected() { #[cfg(debug_assertions)] { if thread::panicking() || !is_active() { return; } PROTECTION_LEVEL .try_with(|v| { let val = { *v.read() }; match val { v if v == 0 => panic!("Attempt to exit protected too many times"), _ => { *v.write() -= 1; } } }) .unwrap_or_else(|_e| ()); } } /// Get the result of an expression, guaranteeing that no memory accesses occur /// during its evaluation. /// /// **Example**: /// /// ```rust /// use qadapt::assert_no_alloc; /// use qadapt::QADAPT; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// fn main() { /// assert_no_alloc!(2 + 2); /// } /// ``` /// /// **Warning**: Unexpected behavior will occur when using the `return` keyword. /// Because QADAPT doesn't have an opportunity to clean up, there may be a panic /// in code that was not intended to be allocation-free. The compiler will warn you /// that there is an unreachable statement if this happens. /// /// ```rust /// use qadapt::assert_no_alloc; /// use qadapt::QADAPT; /// use std::panic::catch_unwind; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// fn early_return() -> usize { /// assert_no_alloc!(return 8); /// } /// /// fn main() { /// let x = early_return(); /// /// // Even though only the `early_return` function contains /// // QADAPT allocation guards, this triggers a panic: /// // `Box::new` forces an allocation, and QADAPT still thinks /// // we're in a protected region because of the return in `early_return()` /// # if qadapt::is_active() { /// let res = catch_unwind(|| Box::new(x)); /// assert!(res.is_err()); /// # } /// } #[macro_export] #[deprecated( since = "1.0.3", note = "Please use the `alloc_counter` crate instead." )] macro_rules! assert_no_alloc { ($e:expr) => {{ ::qadapt::enter_protected(); let e = { $e }; ::qadapt::exit_protected(); e }}; } /// Get the current "protection level" in QADAPT: calls to `enter_protected() - exit_protected()`. /// /// **Note**: For release builds, `protection_level()` will always return 0. /// /// **Example**: /// /// ```rust /// use qadapt::enter_protected; /// use qadapt::exit_protected; /// use qadapt::QADAPT; /// use qadapt::protection_level; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// fn main() { /// # if qadapt::is_active() { /// enter_protected(); /// // We're now in an allocation-protected code region /// assert_eq!(1, protection_level()); /// /// enter_protected(); /// // We're still memory protected, but we'll now need to exit twice to be safe /// assert_eq!(2, protection_level()); /// exit_protected(); /// exit_protected(); /// # } /// /// // It's now safe to allocate/drop /// } #[deprecated( since = "1.0.3", note = "Please use the `alloc_counter` crate instead." )] pub fn protection_level() -> usize { PROTECTION_LEVEL.try_with(|v| *v.read()).unwrap_or(0) } /// Determine whether QADAPT will trigger thread panics if an allocation happens /// during protected code. This should be used for making sure that QADAPT is /// properly set up and initialized. /// /// Note that this will return `false` in release builds even if QADAPT is set /// as the `#[global_allocator]`. /// /// **Example**: /// /// ```rust /// use qadapt::is_active; /// use qadapt::QADAPT; /// /// #[global_allocator] /// static Q: QADAPT = QADAPT; /// /// pub fn main() { /// # if qadapt::is_active() { /// assert!(is_active()); /// # } /// } /// ``` #[deprecated( since = "1.0.3", note = "Please use the `alloc_counter` crate instead." )] pub fn is_active() -> bool { if cfg!(debug_assertions) { // Because there are heap allocations that happen before `fn main()`, // we don't need to force an extra allocation here to guarantee that // IS_ACTIVE is set *IS_ACTIVE.read() } else { false } } fn claim_internal_alloc() { loop { match INTERNAL_ALLOCATION.write() { ref mut lock if **lock == usize::max_value() => { **lock = thread_id::get(); break; } _ => (), } } } fn release_internal_alloc() { match INTERNAL_ALLOCATION.write() { ref mut lock if **lock == thread_id::get() => **lock = usize::max_value(), _ => panic!("Internal allocation tracking error"), } } fn alloc_immediate() -> bool { thread::panicking() || *INTERNAL_ALLOCATION.read() == thread_id::get() } unsafe impl GlobalAlloc for QADAPT { unsafe fn alloc(&self, layout: Layout) -> *mut u8 { if !*IS_ACTIVE.read() { *IS_ACTIVE.write() = true; } // If we're attempting to allocate our PROTECTION_LEVEL thread local, // just allow it through if alloc_immediate() { return SYSTEM_ALLOC.alloc(layout); } // Because accessing PROTECTION_LEVEL has the potential to trigger an allocation, // we need to acquire the INTERNAL_ALLOCATION lock for our thread. claim_internal_alloc(); let protection_level: Result<usize, ()> = PROTECTION_LEVEL.try_with(|v| *v.read()).or(Ok(0)); release_internal_alloc(); match protection_level { Ok(v) if v == 0 => SYSTEM_ALLOC.alloc(layout), Ok(v) => { // Tripped a bad allocation, but make sure further memory access during unwind // doesn't have issues PROTECTION_LEVEL.with(|v| *v.write() = 0); panic!( "Unexpected allocation for size {}, protection level: {}", layout.size(), v ) } Err(_) => unreachable!(), } } unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) { if alloc_immediate() { return SYSTEM_ALLOC.dealloc(ptr, layout); } claim_internal_alloc(); let protection_level: Result<usize, ()> = PROTECTION_LEVEL.try_with(|v| *v.read()).or(Ok(0)); release_internal_alloc(); // Free before checking panic to make sure we avoid leaks SYSTEM_ALLOC.dealloc(ptr, layout); match protection_level { Ok(v) if v > 0 => { // Tripped a bad drop, but make sure further memory access during unwind // doesn't have issues PROTECTION_LEVEL.with(|v| *v.write() = 0); panic!( "Unexpected deallocation for size {}, protection level: {}", layout.size(), v ) } _ => (), } } }